Data storage systems including data storage media such as disc drives are commonly used in a wide variety of devices to store large amounts of data in a form that can be made readily available to a user. While commonly used in computing devices such as personal computers, workstations, and laptops, disc drives have also been incorporated into personal music devices and in other applications.
In general, a disc drive includes one or more storage discs that are rotated by a spindle motor. The surface of each of the one or more storage discs is divided into a series of data tracks. The data tracks are spaced radially from one another across a band having an inner diameter and an outer diameter. The data tracks extend generally circumferentially around the disc and can store data in the form of magnetic transitions within the radial extent of a given track. An interactive element, such as a magnetic transducer, is used to sense the magnetic transitions to read data from the given track. In addition, the interactive element can transmit an electric signal that causes a magnetic transition on the disc surface to write data to the given track.
The interactive element is mounted to an arm of an actuator. The interactive element is then selectively positioned by a control system that causes the actuator arm to be positioned over a given data track of the disc to either read data from or write data to the given data track of the disc, as the disc rotates adjacent the transducer. The actuator arm is typically mounted to a voice coil motor that can be controlled by the control system to move the actuator arm relative to the disc surface.
The nature of disc drives is such that it is advantageous to be able precisely position the interactive element in a desired position to read or write data. Typical servo actuator control systems include a number of different control stages, including a seek stage, a settle stage, and a track following stage. Each control stage is designed to perform a particular function related to the control of the position of the interactive element depending upon the desired positioning action at a particular time. For example, the seek stage is designed to move the interactive element from one location to another, such as when it is desired to read data from or write data to a particular track. The settle stage is designed to stabilize the actuator after a seek action has been performed and transition the control system to the track following stage. The track following stage is typically designed to cause the interactive element to follow the particular track over which it is positioned.
During the manufacture of disc drives, it can be advantageous to calibrate the control system to reduce positioning error that may occur due to a variety of factors, including variability of components and/or manufacturing processes from one control system to the next. For example, calibrating the control system during the seek stage typically provides for more accurate seek operations, which, in turn, provides for more efficient operation of the disc drive system.